Hot melt adhesive composition

Abstract

A hot melt adhesive composition includes ethylene vinyl acetate copolymer(s) having average vinyl acetate content of from about 10% to about 30%, styrene-ethylene-butylene-styrene block copolymer, tackifying resin, and optionally, a plasticizer or a wax.

Description

[0001] The invention relates to a hot melt adhesive composition including ethylene vinyl acetate copolymer(s), styrene-ethylene-butylene-styrene block copolymer, tackifying resin, and optionally plasticizer(s) and / or wax. [0002] Hot melt adhesives have been used for the construction of disposable articles such as disposable diapers, sanitary napkins, surgical drapes, hospital pads, and adult incontinent products, etc. Disposable articles are typically composed of several components that are bonded together by various hot melt adhesives. Depending on the function of components the hot melt adhesives used for bonding one component of the article may be completely unsuitable for bonding another component of the article. [0003] One particular component of the disposable article includes a polyolefin film e.g., a polyethylene or polypropylene film, bonded to a tissue or nonwoven substrate through a hot melt construction adhesive to form a leakage-prevention sheet to prevent permeation of...

AI Technical Summary

Benefits of technology

[0003] One particular component of the disposable article includes a polyolefin film e.g., a polyethylene or polypropylene film, bonded to a tissue or nonwoven substrate through a hot melt construction adhesive to form a leakage-prevention sheet to prevent permeation of fluids. It is desirable that hot melt adhesives used therein would have very good adhesion to nonwoven substrates, high heat stability, proper open time, flexibility, odorless and colorless. Low viscosity is also desirable for low temperature application. Lower application temperature makes it possible to use lighter weight and lower melting films in disposable articles.

[0014] The present invention features a hot melt adhesive composition that exhibits very well balanced properties such as good and consistent compatibility, low viscosity, high heat stability, good adhesion, good cohesive strength, and substantially free of bleed through.

[0017] The adhesive composition exhibits good cohesive strength. In some embodiments, the adhesive composition exhibits initial fine line peel strength of no less than about 70 grams. In other embodiments, the adhesive composition exhibits initial fine line peel strength of no less than about 80 grams. In some embodiments, the adhesive composition exhibits initial fine line peel strength of no less than about 90 grams.

Problems solved by technology

Depending on the function of components the hot melt adhesives used for bonding one component of the article may be completely unsuitable for bonding another component of the article.

While providing the desirable heat stability and flexibility to the bonded substrates, ethylene vinyl acetate copolymer based hot melt construction adhesives exhibit insufficient adhesion in spray applications.

They also tend to build viscosity slowly as they cool causing application problems.

Namely bleeding or soaking through the nonwoven substrate and causing adhesive build up on the machines.

However formulations that have low enough viscosities to be applied at low application temperatures such as no greater than about 135° C. tend to contain a high amount of liquid plasticizer causing these adhesives to be cohesively weak and have a tendency to continue to flow at room temperature or slightly above room temperature.

This can cause disposable articles to stick together under storage or shipping conditions.

Therefore, the two different copolymers have been considered as incompatible.

Without the desirable compatibility, it has been a challenge in the art to formulate a hot melt adhesive including both ethylene vinyl acetate copolymer and styrenic block copolymer that is not only compatible but also has well balanced properties such as desirable heat stability, low viscosity suitable for applications at low temperatures, high adhesion and cohesive strength, as well as no bleed through.

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